JP7183687B2 - balun transformer - Google Patents

Description

The present invention relates to a balun transformer.

In set-top boxes and the like, balun transformers are used for signal conversion between single-ended mode and differential mode between coaxial cables and electronic circuits. When it is necessary to support a wide band from low frequencies to high frequencies, for example, a ferrite core having an elliptical columnar end surface and a pair of through holes having openings on both end surfaces is used. , a wound-formed balun transformer is commonly used.

For example, Patent Literature 1 proposes a transmission line transformer in which a core has a movable portion and two combined wires are wound around the core. The transmission line transformer of Patent Document 1 is supposed to be able to easily adjust the impedance characteristics.

JP 2010-135393 A

With set-top boxes, the frequency band of signals has expanded to higher frequencies due to higher image definition. For this reason, balun transformers used in these devices are required to be usable up to higher frequencies. So far, in order to increase the frequency of the balun transformer, in addition to optimizing the material and shape of the core, for example, winding methods such as reducing the number of turns have been studied. However, if the number of turns is reduced in order to cope with higher frequencies, there will be limited room for consideration of the winding method. SUMMARY OF THE INVENTION An object of the present invention is to provide a balun transformer having excellent high-frequency characteristics.

A columnar core provided with a pair of through holes having openings in a first end surface and a second end surface facing each other; A balun transformer with two conductors. Both ends of the first conductive wire are drawn out to the first end surface side, and both ends of the second conductive wire are drawn out to the second end surface side. Each of the first conducting wire and the second conducting wire has a first planar portion and a second planar portion extending in the longitudinal direction and facing each other. The first conductor is wound with the first flat portion facing the winding axis to form a first coil, and the second conductor is wound with the first flat portion facing the second flat portion of the first conductor. wound to form a second coil, or the first conductor is wound with the first plane portion or the second plane portion crossing the winding axis direction to form a first coil, and the second conductor wire is is wound with the first flat portion facing either the first flat portion or the second flat portion of the first conductor wire to form a second coil.

According to the present invention, it is possible to provide a balun transformer with excellent high frequency characteristics.

1 is a see-through perspective view of a balun transformer according to Example 1. FIG. 1 is an equivalent circuit diagram of a balun transformer according to Example 1. FIG. 2 is a cross-sectional view of the core portion of the balun transformer according to Example 1. FIG. FIG. 10 is a see-through perspective view of a balun transformer according to a second embodiment; FIG. 5 is a cross-sectional view of a core portion of a balun transformer according to Example 2; 7 is a graph showing the insertion loss of the balun transformer according to Example 2; 9 is a graph showing the return loss of the balun transformer according to Example 2. FIG. FIG. 5 is a cross-sectional view of a modification of the through hole of the core of the balun transformer; FIG. 5 is a cross-sectional view of a modification of the through hole of the core of the balun transformer; FIG. 5 is a cross-sectional view of a modification of the through hole of the core of the balun transformer; FIG. 11 is a cross-sectional view of a core portion of a balun transformer according to Example 7; FIG. 11 is a see-through perspective view of a balun transformer according to an eighth embodiment;

A balun transformer of the present invention includes a columnar core provided with a pair of through-holes having openings in first and second end surfaces facing each other, and a portion between the pair of through-holes. a first conductor and a second conductor that are connected to each other; Both ends of the first conducting wire are drawn out to the first end surface side, and both ends of the second conducting wire are drawn out to the second end surface side. Each of the first conducting wire and the second conducting wire has a first planar portion and a second planar portion extending in the longitudinal direction and facing each other. The first conductor is wound with the first flat portion facing the winding axis to form a first coil, and the second conductor is wound with the first flat portion facing the second flat portion of the first conductor. wound to form a second coil, or the first conductor is wound with the first plane portion or the second plane portion crossing the winding axis direction to form a first coil, and the second conductor wire is is wound with the first flat portion facing either the first flat portion or the second flat portion of the first conductor wire to form a second coil.

By forming the first coil and the second coil by winding the first conducting wire and the second conducting wire having the flat portions facing each other with the flat portions facing each other, the coupling between the first coil and the second coil is high. Become. As a result, a balun transformer having excellent high frequency characteristics can be constructed.

The balun transformer of the present invention may further include a plate-like base. The core may be mounted on the surface opposite to the mounting surface side of the base. Each of the ends of the first conducting wire and the second conducting wire may be pulled out to the mounting surface side of the base to form an external terminal. By using a base in which metal terminals are not embedded, members can be omitted and the cost can be reduced.

Each width of the first conductor and the second conductor may be greater than 50% and less than 100% of the maximum length in the direction of the winding axis at the opening of the through hole, or perpendicular to the winding axis It may be greater than 50% and less than 100% of the maximum directional length. As a result, winding collapse is suppressed, and the flat portion of the first conductor wire and the flat portion of the second conductor wire can be wound so as to more reliably face each other and overlap each other. As a result, variations in frequency characteristics can be suppressed.

The balun transformer of the present invention may further include a third conductor wound around the portion between the pair of through holes. Both ends of the third conducting wire may be pulled out to the first end face side. The third conductor may have two plane portions extending in the length direction and facing each other. The third conductor may be wound with one of its planar portions opposed to the second planar portion of the second conductor to form a third coil. Thereby, a balun transformer having an intermediate tap can be easily constructed.

In the balun transformer of the present invention including the third conductor, one end of the first conductor and one end of the third conductor may be electrically connected. This facilitates the construction of a balun transformer with an intermediate tap.

The balun transformer of the present invention including the third conducting wire may further include a plate-shaped base. The core may be mounted on the surface opposite to the mounting surface side of the base. Each of the ends of the first conductor, the second conductor, and the third conductor may be led out to the mounting surface side of the base to form an external terminal. Since the external terminals are formed from the ends of the first, second, and third conductors, a base in which no metal terminals are embedded can be used, and the cost can be reduced by omitting members.

In the balun transformer of the present invention including the third conductor, each of the widths of the first conductor, the second conductor, and the third conductor is greater than 50% of the maximum length in the winding axial direction at the opening of the through hole. It may be less than 100%. Alternatively, it may be more than 50% and less than 100% of the maximum length in the direction orthogonal to the winding axis. As a result, collapse of the winding is suppressed, and it is possible to more reliably overlap the plane portions of the conductor wires. As a result, variations in frequency characteristics can be suppressed.

The balun transformer of the present invention may have two flat portions extending in the penetrating direction of the through holes between the pair of through holes, and the two flat portions are arranged to face each other. may be Since the portion between the through-holes around which the conductive wire is wound has the flat portion, the winding collapse of the conductive wire having the flat portion is further suppressed. As a result, variations in frequency characteristics are further suppressed, resulting in excellent productivity.

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. However, the embodiments shown below are examples of balun transformers for embodying the technical idea of the present invention, and the present invention is not limited to the balun transformers shown below. It should be noted that the members shown in the claims are by no means limited to the members of the embodiment. In particular, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments are not intended to limit the scope of the present invention, but are merely illustrative examples, unless otherwise specified. It's nothing more than Note that the sizes and positional relationships of members shown in each drawing may be exaggerated for clarity of explanation. Furthermore, in the following description, the same names and symbols indicate the same or homogeneous members, and detailed description thereof will be omitted as appropriate. Furthermore, each of the elements constituting the present invention may be configured with the same member so that a single member may serve as a plurality of elements, or conversely, the function of one member may be performed by a plurality of members. It can also be realized by sharing. In addition, the embodiments are shown separately for the sake of convenience in consideration of the explanation of the main points or the ease of understanding, but the configurations shown in different embodiments can be partially replaced or combined. In the second and subsequent embodiments, the description of matters common to the first embodiment will be omitted, and only the points of difference will be described. In particular, similar actions and effects due to similar configurations are not sequentially referred to for each embodiment.

(Example 1)
A balun transformer 100 of Example 1 will be described with reference to FIGS. 1 to 3. FIG. FIG. 1 is a see-through perspective view of the balun transformer 100. FIG. FIG. 2 is an equivalent circuit diagram of the balun transformer 100. As shown in FIG. FIG. 3 is a cross-sectional view of the core 20 of the balun transformer 100 taken along line AA of FIG.

In FIG. 1, the balun transformer 100 includes a columnar core 20 provided with a pair of through holes 23 having openings in a first end face 21a and a second end face 21b facing each other, and a gap between the pair of through holes. It includes a first conductor 11a, a second conductor 12a and a third conductor 13a (hereinafter collectively referred to simply as "conductors") wound around the portion 24, and a base 30a on which the core 20 is placed. The pair of through-holes 23 are arranged with their penetrating directions substantially parallel to each other, and have a substantially circular cross-sectional shape perpendicular to the penetrating direction. The core 20 has an outer peripheral portion 25 surrounding the through holes 23 and a portion 24 between the pair of through holes separating the through holes 23 and around which the conductive wire is wound. Therefore, the portion 24 between the pair of through holes around which the conductive wire is wound is sandwiched between the two arc portions. The core 20 is made of, for example, a ferrite material such as nickel-zinc or manganese-zinc. Also, the size of the through hole 23 may be appropriately selected according to the width of the conductor wire to be wound.

The first conducting wire 11a, the second conducting wire 12a and the third conducting wire 13a are each a conductive wire that is insulated and coated with a thermoplastic resin such as polyurethane. The first conducting wire 11a, the second conducting wire 12a, and the third conducting wire 13a extend in the longitudinal direction and face each other with a first plane portion p1 and a second plane portion p2, and a first plane portion p1 and a second plane portion p1, respectively. It has two planar side portions s1 and s2 adjacent to the portion p2, and has a substantially square cross section. Both ends of the first conductor wire 11a are pulled out toward the first end surface 21a, and the first flat portion p1 faces the winding axis Z, and the first conductor wire 11a is wound one turn around the portion 24 between the pair of through holes. It is turned to form the first coil 7 . Both ends of the second conducting wire 12a are pulled out toward the second end face 21b side, and the first plane portion p1 is directed toward the second plane portion p2 of the first conducting wire 11a, and the portion 24 between the pair of through holes is formed. to form the second coil 8. Both ends of the third conducting wire 13a are pulled out toward the first end surface 21a side, and the first plane portion p1 is directed toward the second plane portion p2 of the second conducting wire 12a, and the portion 24 between the pair of through holes is formed. to form the third coil 9 . That is, the first conducting wire 11a, the second conducting wire 12a, and the third conducting wire 13a are wound around the portion 24 between the pair of through-holes with their flat portions opposed to each other. Here, winding one turn means that the conducting wire passes through one through hole from one end face side to the other end face side, and then passes through the other through hole from the other end face side to the one end face side in the opposite direction. means passed through.

The base 30a is formed in a plate shape from a thermosetting resin such as diallyl phthalate. The base 30a has an upper surface on which the core 20 is placed, a mounting surface facing the upper surface, and four side surfaces adjacent to the upper surface and the mounting surface. Three external terminals 1, 2 and 3 are provided on the side of the first end surface 21a among the opposing side surfaces of the base 30a, and at least the external terminals 4 and 6 are provided on the side of the second end surface 21b. . One end of the first conducting wire 11a is connected to the external terminal 1, the other end of the first conducting wire 11a and one end of the third conducting wire 13a are connected to the external terminal 2, and the external terminal 3 is connected to the other end of the third conductor 13a. The ends of the second conducting wires 12a are connected to the external terminals 4 and 6, respectively. External terminals 1, 2, 3, 4 and 6 are each formed by plating a metal such as copper with tin and nickel. Laser welding, solder dipping, or the like is used to connect the conductors to the external terminals.

FIG. 2 is an equivalent circuit of the balun transformer 100, and black dots in FIG. 2 indicate the winding start of the coil. As shown in FIG. 2, the end of the winding start side of the first conductor 11a is connected to the external terminal 1 and is wound for one turn, and the end of the winding end is connected to the external terminal 2. As shown in FIG. The end of the winding start side of the third conducting wire 13 a is connected to the external terminal 2 and wound for one turn, and the end of the winding end is connected to the external terminal 3 . The end of the second conductive wire 12 a on the winding start side is connected to the external terminal 4 and wound for three turns, and the winding end side is connected to the external terminal 6 . That is, the first conductor, the third conductor, and the second conductor are wound in the same direction. The first conducting wire 11a and the third conducting wire 13a form the primary side of the balun transformer 100, which has the external terminal 2 as a center tap and the external terminals 1 and 3. The second conducting wire 12a forms the external terminal 4 and the external terminal. The secondary side of the balun transformer 100 which consists of the terminal 6 is comprised. As a result, for example, a balun transformer having an impedance ratio of 1:2 is configured with a primary side of 37.5Ω and a secondary side of 75Ω. Further, for example, one of the primary sides and the center tap of the secondary side are grounded and used to configure a balun transformer with a differential mode on the primary side and a single end mode on the secondary side.

3 is a cross-sectional view of core 20 taken along line AA in FIG. 1 and parallel to the end face of core 20. FIG. The first conducting wire 11 a is wound for one turn with the first plane portion p 1 opposed to the winding axis Z to form the first coil 7 . The second conducting wire 12a is wound one turn with the first flat portion p1 facing the second flat portion p2 of the first conducting wire 11a, and then wound three turns with the side portion s1 and the side portion s2 facing each other. to form the second coil 8 . The third conductor 13a forms the third coil 9 by winding one turn with the first plane portion p1 facing the second plane portion p2 of the second conductor 12a.

It can be seen that in the balun transformer 100, the conductors forming the coils have flat portions and are wound in such a manner that the flat portions of the respective conductors face each other, thereby increasing the coupling coefficient between the coils. A balun transformer with a large coupling coefficient can achieve excellent high frequency characteristics. It can be verified by simulation, for example, that the difference in the cross-sectional shape of the conductor affects the coupling coefficient between the coils. Table 1 shows the balun transformer (Example 1) in which the balun transformer 100 shown in FIGS. Regarding the simulation model (comparative example 1) of the balun transformer configured similarly to the transformer 100, the coupling coefficient (K1-2) between the first coil 71 and the second coil 81, the coupling between the first coil 71 and the third coil 91 The results of simulating the coefficient (K1-3) and the coupling coefficient (K2-3) between the second coil 81 and the third coil 91 are shown. The simulation was performed by harmonic magnetic field analysis at a frequency of 10 MHz using finite element method analysis software Femtet (registered trademark) manufactured by Murata Software.

As shown in Table 1, the balun transformer of Example 1, in which a conducting wire with a square cross-section is used and wound with the plane portions of the conducting wire opposed to each other to constitute a balun transformer, is wound with a conducting wire with a circular cross-section. The coupling coefficient between the coils becomes larger than that of Comparative Example 1 configured with

The balun transformer 100 has, for example, a core 20 made of a nickel-zinc ferrite material, and has a columnar shape with an oval end surface. The size of the core 20 is, for example, 5.2 mm long diameter×3.0 mm short diameter×3.0 mm high. Moreover, the cross-sectional shape of the through-hole is, for example, a circle with a diameter of 1.2 mm. The conducting wire of Example 1 is a square with one side of 0.2 mm square, and the conducting wire of Comparative Example 1 is circular with a diameter of 0.2 mm.

(Example 2)
The balun transformer 110 of Example 2 will be described with reference to FIGS. 4 and 5. FIG. 4 is a partially transparent perspective view of the balun transformer 110. FIG. FIG. 5 is a cross-sectional view of the core 20 of the balun transformer 110. As shown in FIG. In the balun transformer 110, the conductive wire has a substantially rectangular cross-sectional shape, the second conductive wire 12b is laminated and wound, and the base 30b does not have an external terminal, and the conductive wire is drawn out to the mounting surface side. It is configured in the same manner as the balun transformer 100 except that it constitutes an external terminal.

In FIG. 4, each of the first conducting wire 11b, the second conducting wire 12b and the third conducting wire 13b has a substantially rectangular cross section, and the longer sides of the rectangle extend in the length direction to form the first plane portion p1 and the second plane portion p1 and the second plane portion p1. A portion p2 is formed, and the short sides extend in the longitudinal direction to form side portions s1 and s2. The aspect ratio, which is the ratio of the length of the long side to the length of the short side in the cross section of the conductor, is, for example, 4 or more. Both ends of the first conductor 11b and the third conductor 13b are drawn out toward the first end surface 21a, and the drawn-out ends are arranged on the side surface and the mounting surface of the base 30b to form external terminals. One end of the first conductor 11b, for example, the winding end, is connected to one end of the third conductor 13b, for example, the winding start, to form one external terminal. Both ends of the second conducting wire 12b are drawn out toward the second end surface 21b, and the drawn-out ends are arranged on the side surface and the mounting surface of the base 30b to form external terminals.

The first conducting wire 11b is wound one turn to form the first coil 72 with the first flat portion p1 facing the winding axis Z with respect to the portion 24 between the pair of through holes. The second conductor wire 12b is wound one turn with the first plane portion p1 facing the second plane portion p2 of the first conductor wire 11b with respect to the portion 24 between the pair of through-holes. The second coil 82 is formed by stacking the portion p1 on the second plane portion p2 and winding two turns for a total of three turns. The third conductor 13b is wound by one turn with the first plane portion p1 facing the second plane portion p2 of the second conductor 12b with respect to the portion 24 between the pair of through-holes. to form

5 is a cross-sectional view of core 20 taken along line BB in FIG. 4 and parallel to the end face of core 20. FIG. In FIG. 5, the second conductor wire 12b is wound so that the plane portion of the first conductor wire 11b overlaps the plane portion, and the third conductor wire 13b is wound so that the plane portion of the second conductor wire 12b overlaps the plane portion. be done. As a result, one layer of the first conductor 11b, three layers of the second conductor 12b, and one layer of the third conductor 13b are laminated. As a result, the balun transformer 110 has a large coupling coefficient between the coils, and exhibits excellent high-frequency characteristics. In addition, since the cross-sectional shape of the conductive wire is rectangular, it is possible to suppress winding collapse, suppress variation in characteristics, and improve productivity. Furthermore, since the conductor wire is wide, the conductor wire itself can form an external terminal.

As shown in FIG. 5, the through hole in the core 20 has a substantially circular cross-sectional shape. The size of the opening of the through hole is defined by the maximum length h in the direction of the winding axis and the maximum length d in the direction orthogonal to the winding axis. The width w of the first conducting wire 11b, the second conducting wire 12b, and the third conducting wire 13b may be greater than 50% and less than 100% of the maximum value h of the length in the winding axial direction at the opening of the through hole, It is preferably 60% or more and 80% or less. As a result, the conductive wire can be wound so that the flat portions face each other more reliably and overlap each other. In addition, the total thickness of the conductor wire wound between the pair of through-holes is more than 50% and less than 100% of the maximum length d in the direction orthogonal to the winding axis at the opening of the through-holes. may be

Table 2 shows the results obtained by simulation of the coupling coefficients between the coils in the balun transformer 110 . Table 2 shows the case where the balun transformer shown in FIG. 4 (Embodiment 2), the coupling coefficient (K1-2) between the first and second coils, the coupling coefficient (K1-3) between the first and third coils, The coupling coefficient (K2-3) of the 2nd coil and the 3rd coil is shown.

As shown in Table 2, it can be seen that the coupling coefficient is almost the same whether the cross section of the conductor is square or rectangular.

The balun transformer 110 has, for example, a core 20 made of a nickel-zinc ferrite material, and has a columnar shape with an oval end face. The size of the core 20 is, for example, 5.2 mm long diameter×3.0 mm short diameter×3.0 mm high. The cross-sectional shape of the through-hole is, for example, a circle with a diameter of 1.2 mm. The conducting wire is, for example, a flat wire having a rectangular conductor cross section of 0.82 mm width×0.085 mm thickness and covered with polyurethane having a thickness of 15 μm. A balun transformer having such a configuration was actually manufactured, and the insertion loss and return loss were measured. For comparison, a round wire having a circular cross section of 0.2 mm diameter and a coating thickness of 6 μm was used as the conducting wire. The insertion loss and return loss with respect to frequency of the balun transformer (comparative example 2) manufactured in 1. were measured. The results are shown in FIGS. 6 and 7. FIG.

FIG. 6 shows a graph of insertion loss S21, and FIG. 7 shows a graph of return loss S11 on the input side. The single-end mode side is the input, and the differential mode side is the output. In FIGS. 6 and 7, the solid line is the result of the balun transformer 110 of Example 2 constructed using flat wire, and the broken line is the result of the balun transformer of Comparative Example 2 constructed using round wire. From the results shown in FIGS. 6 and 7, the balun transformer using rectangular wires greatly improves the insertion loss S21 at 100 MHz or higher and the return loss S11 on the input side at 10 MHz or higher than the balun transformer using round wires. I know you are. Therefore, by using a rectangular wire as a conducting wire, a balun transformer having excellent high-frequency characteristics can be configured.

(Example 3)
The balun transformer of the third embodiment is configured in the same manner as the balun transformer 110 of the second embodiment, except that the number of turns of the second conducting wire is changed from 3 turns to 4 turns.

Since the number of turns of the second conductor is 4 turns, the primary side has a center tap. For example, the primary side is 18.75 Ω and the secondary side is 75 Ω. An excellent balun transformer is constructed.

(Example 4 to Example 6)
The balun transformers of Examples 4 to 6 will be described with reference to FIGS. 8 to 10. FIG. 8 to 10 are cross-sectional views schematically showing cross-sectional shapes of cores 20a, 20b and 20c in balun transformers of Examples 4 to 6, respectively. The balun transformers of Examples 4 to 6 are configured in the same manner as the balun transformer 110 of Example 2, except that the cross-sectional shape of the through hole in the core is different.

In the core 20a of the balun transformer of Example 4, the cross-sectional shape of the through hole is rectangular. In the core 20b of the balun transformer of the fifth embodiment, the cross-sectional shape of the through hole is the rectangular shape shown in the fourth embodiment in which the corners are chamfered. In the core 20c of the balun transformer of Example 6, the cross-sectional shape of the through-hole is arcuate on the side facing the portion 24 between the pair of rectangular through-holes with chamfered corners shown in Example 5. It is roughly semi-elliptical.

In the balun transformers of Examples 4 to 6, the portion 24 between the pair of through holes has two flat portions extending in the direction of penetration of the through holes, and the two flat portions face each other. are placed. If the portion 24 between the through-holes has a flat portion, the conductor wire can be wound with the flat portion facing the flat portion of the portion 24 between the through-holes, which facilitates aligned winding. , the winding state stabilizes. Variation in the characteristics of the balun transformer thus obtained is suppressed.

(Example 7)
A balun transformer of Example 7 will be described with reference to FIG. FIG. 11 is a schematic cross-sectional view schematically showing the wound state of the conductor wire in the core 20 of the balun transformer of Example 7. As shown in FIG. The balun transformer of Example 7 is configured in the same manner as the balun transformer 110 of Example 2, except that the winding state of the conducting wire is different.

In the balun transformer of Example 7, the first conducting wire 11b has both ends pulled out to the first end face side, and is wound for one turn with the first plane portion p1 and the second plane portion p2 intersecting the winding axis Z direction. It is turned to form a first coil. The second conducting wire 12b has both ends pulled out to the second end face side, and is wound three turns with the first plane portion p1 facing the second plane portion p2 of the first conducting wire to form a second coil. Both ends of the third conducting wire 13b are pulled out to the first end face side, and the first flat portion p1 of the third conducting wire 13b is opposed to the second flat portion p2 of the second conducting wire 12b, and the third conducting wire 13b is wound one turn. Form 3 coils.

In the balun transformer of Example 7, the conducting wire is wound around the portion 24 between the pair of through holes with the first plane and the second plane intersecting the winding axis Z direction (so-called edgewise winding). ) to form a coil. As a result, the coupling coefficient between the coils is increased, and a balun transformer having excellent high-frequency characteristics is configured. Moreover, by using a conductor wire having a flat portion, that is, a rectangular wire, it is possible to easily wind the next conductor wire on top of the conductor wire. As a result, collapse of winding is suppressed, variation in characteristics of the obtained balun transformer is reduced, and productivity is improved.

In the balun transformer of Example 7, the width w of the first conducting wire 11b, the second conducting wire 12b, and the third conducting wire 13b is 50% of the maximum value d of the length in the direction orthogonal to the winding axis at the opening of the through hole. It may be larger and less than 100%, preferably 60% or more and 80% or less. As a result, the conductive wire can be wound so that the flat portions face each other more reliably and overlap each other. Further, the total thickness of the conductor wire wound between the pair of through-holes is more than 50% and less than 100% of the maximum value h of the length in the winding axial direction at the opening of the through-holes. good too.

(Example 8)
A balun transformer 120 of Example 8 will be described with reference to FIG. 12 is a partially transparent perspective view of the balun transformer 120. FIG. The balun transformer 120 is configured in the same manner as the balun transformer 110 except that the third conducting wire is not wound and that there is no intermediate tap.

In the balun transformer 120, the first conducting wire 11c and the second conducting wire 12c are wound around the portion 24 between the pair of through-holes with the plane portions facing each other to form a coil. A balun transformer having excellent high-frequency characteristics can be constructed.

In the balun transformer described above, a nickel-zinc-based ferrite material was exemplified as a specific example of the material of the core.
In the balun transformers of Embodiments 2 to 8, the external terminals were formed by the conducting wires themselves, but as in the balun transformer of Embodiment 1, a base in which metal terminals were embedded was used, and the ends were welded by laser welding, solder dipping, or the like. May be connected to a metal terminal.
In the balun transformers of Examples 2 to 8, a rectangular wire having a flat side surface adjacent to the first flat portion and the second flat portion was used as the conducting wire, but the side surface may be a curved surface such as an arc shape. .

100, 110, 120 balun transformers 1, 2, 3, 4, 6 external terminals 7, 71, 72 first coils 8, 81, 82 second coils 9, 91, 92 third coils 11a, 11b first conducting wire 12a, 12b second conducting wires 13a, 13b third conducting wires 20, 20a, 20b, 20c core 23 through hole 24 portion 25 between through holes outer peripheral portion 30a, 30b base p1 first plane portion p2 second plane portion s1, s2 side portion

Claims (4)

A columnar core provided with a pair of through-holes having openings in first and second end surfaces facing each other, and a first conductor wound around a portion between the pair of through-holes ; A second conductor and a third conductor ,
Both ends of the first conductor wire are drawn out to the first end face side, both ends of the second conductor wire are drawn out to the second end face side, and both ends of the third conductor wire are drawn out to the first end face side ,
Each of the first conductor , the second conductor , and the third conductor has a first plane portion and a second plane portion that extend in the length direction and face each other. The width of the three conductors is the same,
The first conductor wire is wound with the first plane portion facing the winding axis to form a first coil, and the second conductor wire has the first plane portion facing the second plane of the first conductor wire. The third conductor is wound with one of the flat portions facing the second flat portion of the second conductor so as to be laminated . or the first conductor wire is wound with the first plane portion or the second plane portion intersecting the winding axis direction to form a first coil, and The two conductor wires are wound so that the first plane portion faces either the first plane portion or the second plane portion of the first conductor wire so as to form a second coil. 3 conductors are wound so that one of the planar portions faces the second planar portion of the second conductor so as to be laminated to form a third coil;
A balun transformer , wherein one end of the first conductor and one end of the third conductor are electrically connected. Equipped with a plate-shaped base,
The core is placed on the surface opposite to the mounting surface side of the base,
2. The balun transformer according to claim 1 , wherein each of ends of said first, second and third conductive wires is led out to the mounting surface side of said base to form external terminals. The widths of the first, second, and third conductors are each the maximum length in the direction of the winding axis or the length in the direction perpendicular to the winding axis at the opening of the through hole. 3. The balun transformer according to claim 1 or 2, which is greater than 50% and less than 100% of the maximum value. 4. The portion between the pair of through-holes has two flat portions extending in the direction of penetration of the through-holes, and the two flat portions are arranged to face each other. a balun transformer as described in

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